J . Phys. Chem. 1994,98, 1695-1703
1695
The Reaction of Hexamethyldisilazane and Subsequent Oxidation of Trimethylsilyl Groups on Silica Studied by Solid-state NMR and FTIR Suvi Haukka'vt**and Andrew Roots Microchemistry Ltd., P.O. Box 45, 021 51 Espoo, Finland, Department of Chemistry, Analytical Chemistry Division, University of Helsinki, Vuorikatu 20, 00014 Helsinki, Finland, and Scientific Services, Analytical Research, Neste Oy, P.O. Box 310, 06101 Porvoo, Finland Received: August 26, 1993; In Final Form: November 1 , 1993"
The reactions of hexamethyldisilazane (HMDS) on silica preheated a t 200-820 OC were carried out using atomic layer epitaxy (ALE), a technique based on saturating gas-solid reactions. This led to highly reproducible numbers of trimethylsilyl groups bonded to the silica surface. The trimethylsilyl groups produced were subsequently oxidized in air with and without bound chromium acetylacetonate complex (SiOCr(acac)2) present. The silica surface at different reaction stages was characterized by carbon determination, 'H M A S N M R , 29Si C P M A S N M R , 13C C P M A S N M R , and FTIR. The reaction with the terminal H-bonded OH groups, in addition to isolated OH groups, on silica preheated a t lower temperatures (
